the-biergarten-app/web/backend/Features/Features.Auth/Commands/RegisterUser/RegisterUserValidator.cs

using FluentValidation;

namespace Features.Auth.Commands.RegisterUser;

/// <summary>
///     Validates <see cref="RegisterUserCommand" /> instances before they are processed.
/// </summary>
public class RegisterUserValidator : AbstractValidator<RegisterUserCommand>
{
    /// <summary>
    ///     Configures validation rules for username format and length, first/last name length, email format and
    ///     length, minimum age based on date of birth, and password strength requirements.
    /// </summary>
    public RegisterUserValidator()
    {
        RuleFor(x => x.Username)
            .NotEmpty()
            .WithMessage("Username is required")
            .Length(3, 64)
            .WithMessage("Username must be between 3 and 64 characters")
            .Matches("^[a-zA-Z0-9._-]+$")
            .WithMessage(
                "Username can only contain letters, numbers, dots, underscores, and hyphens"
            );

        RuleFor(x => x.FirstName)
            .NotEmpty()
            .WithMessage("First name is required")
            .MaximumLength(128)
            .WithMessage("First name cannot exceed 128 characters");

        RuleFor(x => x.LastName)
            .NotEmpty()
            .WithMessage("Last name is required")
            .MaximumLength(128)
            .WithMessage("Last name cannot exceed 128 characters");

        RuleFor(x => x.Email)
            .NotEmpty()
            .WithMessage("Email is required")
            .EmailAddress()
            .WithMessage("Invalid email format")
            .MaximumLength(128)
            .WithMessage("Email cannot exceed 128 characters");

        RuleFor(x => x.DateOfBirth)
            .NotEmpty()
            .WithMessage("Date of birth is required")
            .LessThan(DateTime.Today.AddYears(-19))
            .WithMessage("You must be at least 19 years old to register");

        RuleFor(x => x.Password)
            .NotEmpty()
            .WithMessage("Password is required")
            .MinimumLength(8)
            .WithMessage("Password must be at least 8 characters")
            .Matches("[A-Z]")
            .WithMessage("Password must contain at least one uppercase letter")
            .Matches("[a-z]")
            .WithMessage("Password must contain at least one lowercase letter")
            .Matches("[0-9]")
            .WithMessage("Password must contain at least one number")
            .Matches("[^a-zA-Z0-9]")
            .WithMessage("Password must contain at least one special character");
    }
}